Refractory-oxide incandescent lamp with preheater



Nov. 19, 1968 R. H. ATKINSON ET AL 3,412,286

REFRACTORY-OXIDE INCANDESCENT LAMP WITH PREHEATER Filed Dec. 14. 1966 FIG.3.

A. C- POWER -46 SUPPLY WITNESSES INVENTORS W Russell H. Atkinson M and Heinz 6. Sell ATTORNEY United States Patent 3,412,286 REFRACTORY-OXIDE INCANDESCENT LAMP WITH 'PREHEATER Russell H. Atkinson,-Fanwood,-and Heinz G. Sell, Cedar Grove, N.J.,-.assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 14, 1966, Ser. No. 601,707 8 Claims. (Cl. 315116) ABSTRACT OF THE DISCLOSURE This invention relates to incandescent lamps and more particularly to an incandescent lamp having a refractoryceramic sleeve as its principal source of radiant energy. The lamp of the present invention includes a radiation transmitting outer envelope sealed to a standard threaded base .and includes a pair of lead-in conductors extending from 'said base into the envelope having connected thereto a pair of electrically'parallel circuit means. One'of said pair of circuit means includes a thermal switch and a refractory metal heating filament. The other of said circuit means includes, in series, ballast means and a hollow refractory-ceramic radiator. Upon activation of said lamp said refractory metal heating filament heats said hollow refractory ceramic radiator until said radiator reaches a temperature, which due to its negative resistance characteristic, causes the radiator to become conductive and radiate substantial light in the visible spectrum. For maximum heating efliciency therefractory metal heating filament is axially disposed within the hollow refractoryceramic radiator.

, The lamp industry is continually striving to increase the luminous output'and efiiciency of light sources. These efforts, over the years, have resulted in the introduction of the arc-lamp, the incandescent lamp, the fluorescent lamp, the high-pressure mercury vapor lamp and the highly etficient short are lamp. Each of these types of lamps has its advantages and'disadvantages insofar as luminous intensity, color rendition, power requirements and efficiency are concerned. Conventional incandescent lamps provide radiant energy by passing current directly through a filamentary element thus causing it to glow as a result of the resistance heatingthereof. On the other hand, the fluorescent lamp and the high pressure vapor lampprovideradiationthrough the ionization of an atmosphere disposed between apair of spaced electrodes.

The lamp of the present invention provides a unique source of radiant energy employing the negative resist- :ance characteristics of a refractory-ceramicv in combination with a conventional filamentary radiator to provide a totally new source of radiant energy.

It is an object of the present invention to provide a high intensity incandescent light source.

Another object of the present invention is to provide a self-ballasted high intensity incandescent light source.

A further object of the present invention is the provision of a high intensity incandescent light source which employs a refractory oxide or nitride source as its principal radiating element.

The foregoing objects are accomplished in accordance with the present invention by employing, in a vacuum or inert gas filled, sealed, radiation transmitting envelope, first and second electrical circuits connected in parallel to a pair of lead-in conductors extending through the sealed area of said envelope. The said first circuit includes a starting filament and a switch means, said switch means being operable in response to elevated temperatures within said envelope to render said first circuit inoperative. The second circuit includes ballast means connected in electrical series with a hollow ceramic sleeve which 3,412,286 Patented Nov. 19, 1968 "ice surrounds said starting filament whereby upon the energizing of said starting filament said surrounding ceramic sleeve will be heated to .a sufiicient temperature to permit said sleeve member to become incandescent'and remain incandescent when a predetermined energizing potential is applied across the lead-in conductors.

"The above objects, and others along with many of the attendant advantages of the present invention will become more readily apparent and better understood as the following detailed description is considered in connection with the accompanying drawings, in which:

FIGURE 1 is a side elevation view with a portion of the outer envelope broken away of a lamp constructed in accordance with the present invention;

FIG. 2 is a sectional view taken along the lines IIII of FIG. 1,- and i FIG. 3 is a schematic diagram of the electrical circuitemployed in the present invention. Referring now in detail to the drawings wherein like reference characters represent like parts throughout the several views, there is shown, in FIG. 1, an incandescent lamp generally designated 10 having a radiationtrans mitti-ng outer envelope 12'sealed to a standard threaded base 14. A pair of lead-in conductors 16, 18 -extend through a standard re-entrant stem 20 into the interior of the light-transmitting envelope 12'. A nickel support 22 is also mounted in re-entra nt stem 20 and extends substantially axially of the lamp envelope 12. At its upper end support wire 22 has secured thereto, by means of a glass bead, .a supporting cross-bar member 24. Support wire 22. and cross support member 24 serve to support the separate electrically parallel circuits within the lamp 12. The sealed envelope 12 may enclose either a vacuum or an inert gas such as, for example, argon.

- A first circuit 26 is connected from lead-in conductor 16 to leadin conductor 18 and includes a coiled starting or heating filament of refractory metal 28, as, for example, tungsten, and a thermal switch 30. Thermal switch 30 includes an expansible bellows 32 connected to a resilient contact 34 which operates to disconnect circuit 26 when the temperature within bulb 12 reaches a preselected level. Bellows 32 is filled with an expansible-gas and as the temperature within envelope 12 rises, the gas within bellows 36 expands to break the electrical contact at 37. A second circuit 36 has contained and supported therein a pair of spaced cylindrical refractory 'metal supports 38 having mounted therebetween a ceramic cylinder 40 which surrounds refractory metal filament 28. A pair of ballast filaments 42, 44 are included in the second circuit. Their function will be later described in detail with respect to the operation of said lamp. 7

The lamp of the present'in-vention' is based on the principle that a refractory ceramic such as described has a negative coeflicient of electrical resistance and becomes more conductive at higher temperatures. Zirconium oxide has proven to be especially suitable as a radiator at reasonable lamp temperatures. Although zirconium oxide is preferred, the lamp of the present invention will operate substantially equal-1y as well with other suitable oxides and nitrides, such as magnesium oxide or thorium oxide and boron nitride or silicon nitride. Referring now to FIG. 3 the operation of the lamp will now be described. The block 46 represents a volt AC. power supply or line to which the lamp 10 is connected through a switch 48 and fuses 50. When the lamp is energized, filament 28 heats the interior of the bulb as well as the refractory-ceramic cylinder 40. When the temperature in the refractory-ceramic reaches approximately 1100 to 1200 C., the lamp is designed so that expansion of bellows 32 due to a build-up of pressure therein will operate to open switch 30 causing the circuit '26 to be rendered inoperative. Switch 30 will remain open during operation of the lamp. At the above temperature a refractory-ceramic cylinder 440 of zirconium oxide will be conductive and current through circuit 36 and supports 38 will cause the refractory-ceramic cylinder 40 to continue to remain heated and radiate visible light.

Within moments the refractory-ceramic cylinder will be heated to bright incandescence and would destroy itself if the current through the leads to the cylinder is not limited. For this reason the introduction of a ballast in series with the heating element is necessary. Instead of wasting the energy which is absorbed in the ballast, two filaments 42, 44 are introduced into the circuit 36 and act as ballast. The ballast filaments 42 and 44 are so dimensioned that they become incandescent emitters together with the cylinder mixing the visible radiation produced by each thus adding to the luminous output of the lamp.

As will be apparent starting filament 28 heats the ceramic radiator until it reaches a temperature at which it is substantially electrically conductive at which point switch 30 opens to terminate operation of circuit 26. It will be further apparent that other means may be employed to heat the refractory cylinder 40 beyond a conversion point in its resistance characteristic in order that the refractory-ceramic cylinder will become conductive and hence radiate.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A refractory incandescent lamp comprising.

(a) a sealed radiation transmitting outer envelope confining a vacuum or inert atmosphere;

(b) a pair of lead-in conductors extending through the sealed area of said lamp envelope; and

(c) first and second circuits electrically connected in parallel and connected to said lead-in conductors internally of said envelope, said first circuit including a starting filament and switch means operable in response to elevated temperatures to electrically disconnect said first circuit, said second circuit comprising ballast means connected in electrical series with a hollow ceramic body, said starting filament extending through said ceramic body and adapted to heat said ceramic body until said ceramic body hecomes highly conductive and incandescent.

2. The refractory incandescent lamp according to claim 1 wherein said hollow ceramic body is a cylinder.

3. A refractory incandescent lamp according to claim 2 wherein said-hollow ceramic cylinder consists essential- 1y of zirconium oxide.

4. An incandescent light source comprising: (a) a sealed light transmitting envelope;

(b) an elongated sleeve member supported within said envelope and formed of a refractory ceramic;

(c) lead-in conductors electrically connected to the ends of said sleeve member and sealed through said envelope and adapted to have a predetermined energizing potential applied thereacross to supply electrical energy to said sleeve member; 1

(d) ballast means electrically connected in series with said sleeve member by said lead-in conductors to limit electric current through said sleeve member to a predetermined value, said sleeve member, when heated to a predetermined temperature and energized by applying predetermined potential across said leadin conductors, becoming incandescent and remaining incandescent due to the electrical energy passing said ballast means and dissipated in said sleeve member; and

(e) heater means surround by said ceramic sleeve and adapted to heat said sleeve to said predetermined temperature.

5. An incandescent light source according to claim 4 wherein said heater means comprises an elongated refractory metal member longitudinally extending through said sleeve member, said metal member having a positive temperature coefficient of electrical resistance, and said metal member adapted to be electrically heated to a temperature sufiicient to heat said sleeve member to that predetermined temperature which will permit said sleeve .member to become incandescent and remain incandescent when the predetermined energizing potential is applied across said lead-in conductors.

6. An incandescent light source according to claim 5 wherein said refractory-ceramic sleeve has a high electrical resistance at room temperature, a negative temperature coefficient of electrical resistance, and a relatively low electrical-resistance at incandescent temperatures.

7. An incandescent light source according to claim 6 wherein said refractory-ceramic sleeve consists essentially of at least one material of the group consisting of zirconium oxide, magnesium oxide, thorium oxide, boron nit-ride and silicon nitride.

8. An incandescent light source according to claim 4 which further includes thermal switch means in electrical series with said heater means and responsive to elevated temperatures within said lamp to deactivate said heater means.

References Cited UNITED STATES PATENTS 717,022 12/1902 Potter et a1. 315l16 1,617,633 2/1927 Heany 31547 JAMES W. LAWRENCE, Primary Examiner.

DAVID J. GA-LVIN, Assistant Examiner. 

